Although the present invention can be used in a variety of applications in many different fields, the preferred embodiment is used in the field of sensors or scanners. In the field of sensors or scanners, certain prior art devices have indicators that display a measure of signal strength. Such displays are useful as an aid in correctly aligning the sensor or scanner. For example, in the field of photoelectric sensors, various techniques are used in displaying the strength of the received light signal, such as a variable frequency flashing indicator or a LED bar graph display.
The trend toward miniaturization of sensor and scanner devices has created problems in their electrical design. Miniaturization requires smaller, or alternatively, fewer, electronic components. Miniaturization also complicates the tasks of power supply and heat dissipation because power for low voltage DC circuits often requires the conversion of 120 volt AC. Thus, in miniaturized sensors or scanners, providing both a signal strength indicator and a separate diagnostic indicator in the sensor or scanner would conflict with the need for minimizing the size of the circuit, the power required by the circuit, the amount of heat generated, the number of components used, and the cost.